Is it possible to use an image to edit a mesh to the image's size?
There are two methods I'm thinking of.

The first is using an SVG of the image contour.
Loading the image in Blender Using Import Images As Planes.
Import the SVG.
I converted the SVG to Mesh and applied the same material of the image. 

The second try is using the Knife topology tool ( K ) direct to the imported image to cut the subject. No need for a vector-based program. Delete the unwanted faces.
This method was faster because all is done inside Blender.
Note we have to do short cuts to smooth corners.